ZURICH -- Swiss Reinsurance Ltd. Tuesday increased its estimate of losses arising from the Sept. 11 attack on the World Trade Center by almost 50% and said it now expects to post a loss for 2001.

The Swiss insurance giant raised its estimate of net losses related to Sept. 11 to 2.95 billion Swiss francs ($1.74 billion or two billion euros) from about two billion francs made shortly after the attacks, blaming the stronger dollar and lower expectations of how much it will recover from other insurers. It will take about one...